Thanks for that link Whatcaneyedo. It's appreciated.
I have read RHF's articles about ORP and the caution not to put too much emphasis on absolute readings. That's probably good advice. While I was glad to see a slow upward trend as I made efforts to improve the water quality my line-in-the-sand about not fretting about absolute the readings was 400 mv.
Although that number might sound a bit arbitrary considering RHF states 350-450 mv being 'normal', he also states to code your controller to shut down your ozone generator if readings pass 450 mv. Other discussions at Reef Central state emphatically that it's "impossible" to reach 400 mv without using ozone or adding oxidizing agents to your tank. RHF says just use the probe to measure trends. Well, assuming a 20-50mv margin for error in my probe, I'm still well on my to "impossible", lol. I topped out at 411 this morning. I don't have an ozone generator to shut off.
In the spirit of being proactive I thought I'd start keeping an eye on this. Frankly, I'm having a hard time finding any specific symptoms to watch out for. Aside from vague cautions about not to worry (on one hand) and shutting down ozone after 450mv, (on the other hand) I can't really find specific advice. Why is over 450mv bad? What might it do to my tank's inhabitants? Will my fish grow 3 eyes? Will the corals explode if my wife decide to bless them with holy-water? I'm guessing not. OTOH when I watch my tank tonight and sip my favorite adult beverage, I'm going to back my chair up a few feet....just in case.
